Control system for fluid operated mechanism



5 Sheets-Sheet J.

April 19, 1960 J. L. GRATZMULLER CONTROL SYSTEM FOR FLUID OPERATEDMECHANISM Filed Nov. 2, 1956 II V I vVHUU n um llllll I I ham/An??? l wr v Aprll 19, 1960 J. L. GRATZMULLER 2,933,069

CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5Sheets-Sheet 2 April 19, 1960 J. L. GRATZMULLER 2,933,069

CONTROL SYSTEM. FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5Sheets-Sheet 3 April 9, 1960 .1. L. GRATZMULLER 2,933,069

CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5Sheets-Sheet 4 April 19, 1960 J. L. GRATZMULLER 2,933,069

CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5Sheets-Sheet 5 Izwezvmp 7. .Grwzzmu 6661 2,933,069 Patented Apr. 19,1960 ice 2,933,069 CONTROL SYSTEM FOR FLUID OPERATED MECHANISM JeanLouis Gratzmuller, Paris, France Application November 2, 1956, SerialNo. 620,075 Claims priority, application France November 4, 1955 4Claims. (Cl. 121-38) This invention relates broadly to the art ofelectric control apparatus.

More particularly, the invention relates to circuit-breaking and makingapparatus hereafter called circuit-breakers whatever their specificnature. Still more particularly, the invention is concerned with controlmeans for actuating the movable contact means of a circuit-breaker.

A circuit-breaker has to fulfill two main functions:

1) a permanent function, namely causing high strength currents to passthrough its contacts without excessive heating.

(2) a transient function, namely switching-off or -on currents havingdifferent characteristics (for example, short-circuit currents, capacitycurrents, etc.) and doing so without mishap, either in the apparatus orin the mams.

Now, all known circuit-breakers offer deficiencies preventing them fromensuring satisfactorily either their permanent or their transientfunction, or even both.

Accordingly, it is an object of this invention to provide an improvedcircuit-breaker capable of assuming both the above mentioned functionsin a satisfactory manner.

In particular, the transient function of a circuit-breaker impliesstabilizing of the speed of its movable contact means at each point ofits stroke, at a value comprised between two predetermined limit valueswhich correspond to imperative electrical and mechanical conditions.

On the other hand, as regards the circuit-breaking stroke of the movablecontact means, the same should be subjected to an initial accelerationas strong as possible so as to reduce to a minimum the total duration ofthe current cut-ofi? operation between the separation of the contactsand the complete extinguishment of the are.

It is therefore a further object of the invention to provide, in and fora circuit-breaker, a control device including a source of power capableof imparting to the movable contact means of the circuit-breaker a veryhigh initial acceleration as well as maintaining its speed during itswhole stroke at a value at least equal to a predetermined minimum value,the said device furthermore comprising means to brake the movablecontact means as a function of its own speed, so as to maintain the saidspeed at each point of the stroke under a predetermined maximum value.The above mentioned minimum and maximum values are defined by theelectrical and mechanical conditions to be fulfilled by thecircuit-breaker.

Still another object of the invention is to design the hereabovementioned braking means in such a manner that their action varies as afunction of the speed of the movable contact means according to such alaw that the said action becomes effective but only at a substantialspeed so that it does not practically impair the said in itialacceleration.

Now, in practice, only the accumulation of power by resiliency (elasticdeformation of solids and gases) permits designing, in a practical andnot exceedingly expensive shape, a superabundant and rapidly availablesource of power.

Accordingly, it is a more particular object of the invention to use, asa source of power for each stroke of the movable contact means, aresilient power accumulator such as a spring, a compressed gas, etc.

It has been found that the use of the elasticity of gases, for at leastone of the two opposed operations to be effected, is particularly cheap.

Now, the best known device using the elasticity of gases as a source ofpower, is the oil-and-air accumulator.

In particular, the applicant has described in the US. Patents No.2,724,412, No. 2,746,486 and U. S. Patent application No. 307,863 filedSeptember 4, 1952, now Patent No. 2,804,094, an oil-and-air accumulatorparticularly well adapted to be used for controlling circuit breakers inthe hereabove enumerated conditions.

Consequently, another object of the invention is to use, as a source ofpower for controlling a circuit-breaker in the manner described, anoil-and-air accumulator, preferably of the type described in the abovecited prior application.

A further object of the invention is to provide a circuit breakercontrol device of the type described, wherein a displacement of themovable contact means causes a corresponding displacement of a hydraulicliquid. This latter displacement being obtained, for example, byproviding a permanent kinematic interconnection between the said movablecontact means and one or more hydraulic jacks.

It is one of the main objects of the invention to obtain the requiredregulation of control of the speed of the movable contact means bycontrolling the said liquid displacement.

In this connection, when liquid flows through a conduit, it follows alaw which is comprised between two limits, the law governing laminarflow, and the law governing turbulent flow. if the flow is purelylaminar, that is, with very low speed, the difference in pressurebetween the upstream side and downstream side of any defined zone in theconduit, that is the loss of pressure is proportional to the speed. Itis also proportional to the viscosity. The other limit is in instancesof a purely tubulent flow, turbulent flow corresponding to high speed,great pressure differences, and low viscosity. In such a case, the lawis that the loss of pressure is proportional to the square of the speed.This loss no longer is dependent upon viscosity, and is proportional tothe density.

Accordingly, it is an object of this invention to ensure that thecontrol of the circuit breaker, namely, the braking means therefor is acalibrated permanently open restriction means formed by a sharp-edgedorifice, so as to obtain a law of How in the conduit(s) approaching asnearly as possible the law of the square of the speed. in connectionwith this sharp-edged orifice, it may be defined as a circular orificecut in a thin plate, which results in that the flow in the conduit(s)follows a law much nearly approaching the law of the square of the speedthan to the law of the laminar flow.

With this arrangement, at low speeds, the rate of flow of the liquid ispractically not restricted so that a maximum acceleration is imparted tothe movable contact means while at high speeds, the intensity of thebraking efiect at each point of the stroke is substantially proportionalto the square of the movable contact speed, so that it easily maintainsthe said speed between the suitable limits. This method of controllingthe speed of the movable contact means moreover offers the essentialadvantage of being practically independent of temperature variations,since the rate of flow of a fluid through a sharp-edged orifice is butslightly responsive to variations of viscosity of the said fluid.

In a particular embodiment of the invention, at least for one stroke ofthe movable contact means, the resilientr 3 V ly accumulated powerprovided to ensure the said stroke is transmitted to the said movablecontact means through a liquid and a jack fed with the same under thecontrol of a hydraulic valve. V

A Well-knowndifficulty'of circuit'breaker control is to lock them intheir circuit making position.

It is accordingly a further object of the invention to control bothstrokes of the circuit breaker of the movable contact means by means ofhydraulic valves, all usual mechanical locking means being excluded.

For this purpose, a specific object of the invention is to design thecircuit breaker control device in the manner described in the US. patentapplication Ser. No. 479,620, filed January 3, 1955 in the name of theapplicant.

In this arrangement, the circuit-making stroke, as Well as the lockingin circuit-making position of the movable contact means are effected. bymeans of a single-acting hydraulic jack fed with oil from an oil-and-airaccumulator of the type described, while the circuit-breaking stroke isensured by a spring armed during the circuitmaking stroke and releasedasthe oil contained in the said jack is evacuated at a' sufficientlyhigh rate.

The said arrangement furthermore permits controlling the. speed of themovable contact means during both strokes of the sameby incorporatingone or more calibrated permanently open restriction means formed by asharp-edged orifice in the feeding and evacuation ducts.

of. the jack.

Another advantage of the c'"cuit control device with hydraulictransmission, according to the invention, is that of offering but a verysmall natural inertia. Therefore a control device of this type, capableof generating a superabundant force controlled by calibrated orificesdetermining a well defined stabilized speed with a high initialacceleration, may be easily designed at low cost. Such a control iscapable, in turn, of determining a well defined stabilized speed of themovable contact means, whichever may be the nature of the electrical ormechanical phenomena resisting itsdisplacement.

In particular, it has been mentioned at the beginning of this preamble,thatthe permanent function of a circuit-breaker consists in causing highstrength currents to pass through its contacts without excessiveheating. The hydraulic control according to the invention, which isdescribed above, is capable of generating superabundant driving forcesand hence overcoming considerable resisting stresses, precisely permitsestablishing electrical contacts of a heretofore unknown quality,capable of fulfilling satisfactorily the said permanent function bysubjecting the metal contact members to ahigh contact pressure. I

Since the control device according to the invention permits establishingelectric contacts under a pressure which may be given a heretofore neverused order ofmagnitude and sinceit also permits both imparting to themovable contact means a very high initial acceleration and stabilizingits speed during its whole stroke, the said device offers a possibilityof designing circuit breakers capable of fulfilling in an'entirelysatisfactory manner the above defined permanent and transient function.

Accordingly, still another object of the invention is to provide acircuit breaker equipped with'a control device of the type described andincludingcontacts established under a pressure which maybe chosen ifdesired at a value having the same order of magnitude as the forceavailable in the said device.

Finally, the two main types of contacts adapted to be used in a circuitbreaker are the abutment contacts and thesliding contacts; the firstones offer many drawbacks and tend to be more and more abandoned infavor of the second ones;

It is therefore a more specific object of the invention to provide acircuit breaker equipped with a control de vice of the type describedoperatively connected with a movable contact means, slidably mounted ina connecting inafter described with reference to the accompanying.

drawings, given merely by way of example and 'in which:

Figure 1 is a diagrammatic view in longitudinal section,

of a circuit-breaker according to the invention.

Figure 2 illustrates in a diagrammatic manner a first' embodiment of thehydraulic control device according to the invention, comprising asingle-acting jack with circuit-breaking spring.

Figures 3 and 4 are detail views showing two different constructions ofa calibrated sharp-edged orificeaccording to the invention.

Figure 5 is a modification of Figure 2 showing a modified arrangementof'the calibrated sharp-edged orifices.

Figure 6 is a longitudinal axial sectional view of an oiland-airaccumulator of the type described in the above cited references, whichmay be used as a source of re silient power in the control deviceaccording to the invention.

Figure 7 is an axial sectional view of a spring hydraulic accumulatoralso adapted to be used as a source of resilient power. 1

Figure 8 is an elevational partly sectional view of the contactmechanism of a circuit-breaker according'to the invention. e

Figure 9 is a part sectional view along line 99 of Fig. 8. a

Figure 10 shows a double-acting jack during a circuitbreaking stroke.

Figure 11 shows the same device during a circuitmaking stroke.

Figures 12, 13 and 14 illustrate. modified forms of con struction of thedevice in Figures 10 and 11.

Figure 15 shows anon-differential double-acting jack, supplied by twodifferent sources of pressure.

Figure 16 hows a differential double-acting jack, one compartment ofwhich is constantly in communication with a source of pressure.

Figure 17 is a modification of the form shown in Figure 2 in which onlythe circuit-making stroke of the circuitbreakeris controlled.

Figure 18 is a modification of the form shown in Figure 13 in which onlythe circuit-breakingstroke of the circuitbreaker is controlled.

Figure 1 shows by way. of example, which is,,of course,

non-limiting, a single-pole circuit-breaker which can be controlled by adevice according to the invention. This circuit-breaker comprisesessentially, a movable contact 1- sliding in a contact sleeveZ connectedto one of the conductors 3 of the circuit to be broken. In thecircuitmaking position illustrated, the movable contact 1 isengaged in atulip-shaped fixed contact 4, electrically connected to the otherconductor 5 of the. said circuit. In the example illustrated, themovable contact Iris rigidly connected to a control rod 6 by means of aninsulating member 97. In the usual manner, the. movable contact 1 andthe insulating member 97 are immersed in oil as indicated at 98 and 99respectively.

In all the embodiments illustrated-in Figures 2, 5 and 10 to 18 anddescribed below, it is assumed, by way of simplification, that the rod6. is connectedrdirectly to the piston of a control jack andconsequentlythis rod is indicated on the various figures by the samereference numeral (6) as in'Figure 1. It is obvious that the-inventionisin no way limited to this mode of connection and that any kinematicaldevice, which may or may not be a step-up device, could be interposedbetween the controljack and the rod 6, the gear ratio being variable inthe course of the stroke of the movable contact. Moreover, it would alsobe possible to provide 'a plurality of jacks, for example single-actingjacks, connected to the rod 6 by a kinematical device.

Moreover, in order to simplify the description, it is assumed that theupward stroke of each of the jacks illustrated in Figures 2, 5 and 10 to18, effects the circuitmaking stroke of the circuit-breaker in Figure 1and that the downward stroke of each of said jacks efiects thecircuit-breaking. It is obvious that this arrangement could be reversedwithout in any way changing the hydraulic circuits illustrated.

In the embodiment illustrated in Figure 2, the control of the rod 6 iseffected by a single-acting jack, the cylinder of which is seen at '7and the piston at 8, connected to the rod 6 by its rod 9. At 10 is seena spring adapted, to effect the circuit-breaking stroke as oil isevacuated from the jack 7, while the subjection to pressure of said jacketiects the circuit-making operation. The hydraulic circuit in Figure 2comprises a resilient accumulator of hydraulic power 11 fed by a pump 12from a reservoir, with liquid such as the oil 13. The accumulator l1feeds the jack 7 by means of pipes M, 15 and 16, under the control of avalve 17 of a set of valves 18. The evacuation of the oil from jack 7,takes place through the pipes 16, 19 and 20 under the control of thevalve 21 in the set of valves 18. Still for the sake of simplification,it is assumed that the valves 17 and 21 are controlled by simplepush-buttons 22 and 23 respectively.

According to the invention, in this example, a calibrated permanentlyopen restriction means formed by a sharp-edged orifice 24 is interposedin the path of the liquid under pressure feeding the jack '7 and asecond calibrated permanently open restriction means formed by anothersharp-edged orifice 25 is interposed in the evacuation path of theliquid coming from the jack 7. The orifices 24 and 25 are illustrateddiagrammatically in Figure 2 in the form of simple apertures pierced indiaphragms inserted, in the example illustrated, in the pipes 15 and 19.In Figures 2, 5 and 10 to 18 the calibrated sharp-edged orifices havebeen shown in the shape of a gap in a single solid line. In practiceeach of the orifices may consist of a passage such as 26 (Figure 3)drilled in a member 27 interposed in the path of the liquid to becontrolled.

The power of the speed of the movable contact means, in function ofwhich the intensity of the braking action exerted by the calibratedsharp-edged orifice varies, increases as the ratio between the lengthand the cross section of the passage decreases; the said power tends tobecome equal to 2 as the said ratio tends towards 0.

According to another preferred embodiment, each orifice such as 28 (seeFigure 4) may be drilled in a detachable diaphragm 29 which may, forexample, be held by means of screw-bolts 32, between flanges 30 and 31of two lengths of pipe joined together by the said flanges. This lastarrangement is particularly advantageous and permits designing asharp-edged orifice ensuring a braking intensity practicallyproportional to the square of the speed of the movable contact.

Actually, if x is the distance covered by the movable contact at thestart of its stroke, and u the volume of oil displaced by the jack sincethe start of its stroke, for a given value of x, an elemental volume duwill correspond to an elemental displacement dx. There will be a ratio kbetween a'x and sin and this ratio will be constant if the reduction inmovement between the rnovable contact and the movable member of the jackis constant; said ratio will be variable as a function of x if the saidreduction is not constant; this ratio provides the Formula 1:

dx=k du (1) It v is the speed of the movable contact, e the delivery ofthe jack, there is obtained a relationship expressed by the Formula 2:

tit being the elemental time.

If the flow of liquid were controlled by passing it through a conduithaving its length tending towards inf. co) the loss of p would tendtowards the following limit:

0 being a constant coefificient and m a coefiicient depending on theviscosity of the liquid. For a conduit of a great length the actualvalue of the loss of pressure would be but slightly difierent from thistheoretical value. In the case of calibrated permanently openrestriction means formed by sharp-edged orifices the loss of pressure pis given by the Formula 4:

0 being a coefiicient independent of viscosity. Since the viscosity of aliquid depends on its temperature, it is thus possible to provide a lossof pressure practically independent of the temperature, experienceproving that under these conditions the rate of flow obtained for agiven loss of pressure obeys almost strictly the law of dynamic flow ofa liquid through a theoretic sharp-edged orifice.

By combining the Formulae 3 and 4 on the one hand and 2, on the otherhand, Formulae 5 and 6 are obtained:

p= imv (5) giving in both cases the loss of pressure as a function ofthe speed of the movable contact means of the circuit breaker.

The sharp-edged orifice corresponding to Formula 6 is particularlyadvantageous since it permits a greater initial acceleration than whenthe speed is controlled by means of a long passage. Actually, if pc isthe loss or" pressure corresponding to the stabilized speed, when theinstantaneous speed is equal to /s of the said stabilized speed, theFormula 5 will give a loss of pressure equal to /3 of 20, according toFormula 7:

while Formula 6 (case of sharp-edged orifice) will give a loss ofpressure equal to ,6 of po according to Formula 8:

As a specific illustrative example I have given hereafter thecharacteristics or a 70,000 volt high voltage line circuit-breaker whichis equipped with a control device according to the invention, of thetype described above with reference to Figure 2, the said deviceincluding a hydraulic jack directly acting upon the movable contact rodand which has been found utterly satisfactory for both permanent andtransient functions defined at the beginning of this specification(rating current 1200 amperes, cut-oil? ctu'rent 20,000 amperes).

The control device is equipped with an air-and-oil accumulator of thetype described in the above cited references, having a maximum pressureof about 4,300 p.s.i. and a minimum pressure of about 2,800 p.s.i. Thestrength of the circuit-breaking spring when fully com pressed is about1,100 lbs.

The single connecting jack has a cross section of about .9 sq. in. and astroke (equal to that of the movable con- 7 feeding of the jack and,hence, the circuit-making speed has a diameter of about The calibratedorifice controlling the delivery of the jack and hence thecircuitbreaking speed has a diameterof about The length of bothcalibrated orifices is about The movable contact rod has a diameter ofabout 1 and its weight is about 7 kgs. Themoving parts of the jack weighabout 10 lbs. and the spring has an equivalent mass of about 5 lbs.,which gives an overall weight of the moving assembly of about 22 lbs.

With the specific control device hereabove described, at the beginningof the circuitbreaking stroke, the whole initial strength of the spring,viz. 1,100 lbs. is available. If the frictions after starting areestimated to about 110 lbs, the movablecontact will be actuated by aresultant force of:

1,l00ll0==990 lbs.

so that the said movable contact is subjected to an initial accelerationof:

and after the first /s of its circuit-breaking that correspondssubstantially to the above-mentioned period of initial acceleration, toan average velocity of about -.t3' per second.

In the embodiment shown in Figure 5, the structure of the control jackis identical with that in Figure 2, but a slightly diflerentarrangementis adopted for the hydraulic circuit enabling the calibratedorifices to be interposed in the immediate vicinity of the jack 7. Forthis purpose and inorder to effect the supply and drainage of the liquidthrough a single pipe 33, two non-return valves 3d, are provided,interposed in two branches from the said single pipe 33, namely 36 and37, in which branch pipes the constriction means are likewiseinterposed, being designated respectively by the reference numerals 3%and 39. In the example illustrated, the jack 7 is connected to the twobranch pipes 36 and 37, likewise by means of a single pipe 33a. As aresultof the presence of the non-return valves 34 and 35, the calibratedaperture 38 exclusively controls the drainage delivery, while thecalibrated aperture 39 exclusively controls the supply delivery.

The air-and-oil accumulator shown in Figure 6 is provided with threespecial packing devices, as follows:

(a) as described in the first reference hereabove cited, the piston ofthe accumulator comprises a packing ring 103 made of plastic materialand mounted in an annular groove 104 of the lower face 105 of thepiston. This packing ring is continuously subjected through a pressingmember 101 to'the action of a spring 102 bearing on the upper face 106of the piston and that compresses it axially.

, (b) the air compartment, as described in the second referencehereabove cited, is kept tight by means of a cylinder head 107 freelyfitted at the air side extremity of the cylinder 108 and which isprevented from escaping by means of a nut 109, a packing ring 110 madeof plastic material being interposed between the nut 10% and thecylinder head 107. Under these conditions, the head 107 is pressedagainst the packing ring 110 with a pressure that increases as the airpressure in the accumulator increases.

wardly by means of-a threaded cylinder head 112. The

, 8 V pipe conducting oil from and to the accumulator, is shown at 113.A

This" oil-and-air accumulator maybe used as a source of resilient powerfor actuating the movable contact Another example of a source ofresilient power,

adapted to be used under the same conditions, is the spring hydraulicaccumulator shown in Figure 7. The said spring accumulator essentiallycomprises a cylindrical casing 114 provided with a long axial hollowembossment 115, which acts as a cylinder for a plunger 116 having apacking terminal pad 117. A compression spring 118 compresses the oilcontained in the compartment 119 of the cylinder through a flangedsleeve 120 and the piston 116 on which the said sleeve bears. The spring118 bears at one end on the flange 120a of the sleeve 120 and at itsother end on the head 121 of the cylindrical casing :114. g

In Figures 8 and 9 is shown a circuit-breaker according to the inventionof the general type of Figure l.

The circuit-breaker shown in Figures 8 and 9 differs from all knowncircuit-breakers by the quality of its electrical contacts obtainableonly by the use of the control device with hydraulic transmissionaccording to the invention.

In the example shown the tulip-shaped stationary contact generallydesignated by 4 and the connecting sleeve generally shown at 2, in whichthe movable contact rod 1 is slidably mounted, are both constituted by aplurality of members 122 having the general shape of shoes hearingagainst the cylindrical wall periphery of the said rod around which theyare suitably distributed. Each member 122 is urged towards the axis ofthe rod 1 by a strong compression spring 123 having a high elasticity.

Owing to this arrangement, each member 122 is pressed on the rod 1 witha predetermined force; now, when'two metal surfaces are pressed againsteach other with a predetermined force, the deformation of both contactsurfaces produces a metal-to-metal contact area that depends only on thenature of the metals and the contact pressure. If the latter issufficient there will be obtained a metal-to-metal contact areasuflicient to ensure without excessive heat the passage of the strongelectrical current flowing through the line.

70,000 volt high voltage line circuit-breaker previously described, thepermanent function of which is to ensure" the passage through itscontacts of a rating current of 1200 amperes, the sum of the forcespressing the 'members 122 of each contact 2 and 4, has been chosen equalto about 550 lbs. device hereabove described in which at the beginningof the circuit-breaking stroke a motive power of 1,100 lbs. isavailable, would permit overcoming a static friction resistance of 550lbs. for each contact, so that it permits using an overall force ofcontact pressure having the same value.

Figures 10 and 11 illustrate another embodimentin which the hydrauliccontrol device comprises a doubleacting jack 40, the piston 41 of whichis connected directly to the rod 6, which is rigidly connected to themovable contact to be controlled. In this embodiment, each of thecompartments 42 and 43 of the jack 40 may either be brought intocommunication with a source of liquid under pressure, not illustrated inthis figure, or set to exhaust, the supply to and the drainage from eachof the said compartments being effected through a single pipe, namely44a, 44b, for the compartment 43, and 45a, 45b for the compartment 42,under the control of a set of valves 46 selectively eitecting either thebringing of one pipe 47, connected to the source, into communicationnectcd to exhaust, into communication with the pipe 45a Precisely, thespecific control (Figure 10), or, on the other hand, the simultaneousestablishment of communication between the pipes 47 and 45a on the onehand, and 48 and 44a on the other hand (Figure 11).

The control of the set of valves 46 is illustrated, still by way ofsimplification, in the form of two push-buttons, respectively 49 and 50,the depression of the push-button 49 effecting the establishment of thecommunication described above, illustrated in Figure 10, and determiningthe circuit-breaking stroke of the circuit-breaker, while the depressionof the bush-button 50 determines the establishment of the communicationsdescribed above, illustrated in Figure 11 and determining thecircuit-making stroke of the circuit-breaker.

In the embodiment shown in Figures 10 and 11, the calibrated orifices 51and 52 are respectively provided in the non-return valves 53 and 54, thedirection of action of said non-return valves being selected in such amanner that the calibrated apertures 51 and 52 only control the drainagefrom the compartments 43 and 42 respectively.

Figure 12 illustrates a modified form of construction of the devicewhich has just been described with reference to Figures 10 and 11, andonly differs therefrom in the direction of action of the non-returnvalves 53 and 54, this direction being chosen in such a manner that thecalibrated orifices 51 and 52 only control the supply delivery to thecompartments 43 and 42 respectively.

Figure 13 illustrates another modification of the device in Figures 10to 12, in which only the compartment 42 of the double-acting jack iscontrolled. In the example illustrated, this control affects both thesupply delivery to said compartment by means of a calibrated orifice 55,and the drainage delivery from the said compartment by means of acalibrated orifice 56. Non-return valves, 57 and 58 respectively, areprovided to prevent the supply delivery from passing through the orifice56 and the drainage delivery from passing through the orifice 55.

Figure 14 illustrates an inverted arrangement of Fig ure 13, that is tosay in which only the compartment 43 of the jack is controlled, thecontrol applying, in this example again, both to the supply and to thedrainage.

In Figure 15, the device comprises a doubleacting jack 59, which isnon-difierential, that is to say in which the piston 60 is provided withtwo opposed rods 61, 62 which are of the same cylindrical section, therod 61 being assumed to be connected to the rod 6 of the circuit-breakerin Figure 1, for example. One of the compartments, 63, of the said jackis permanently connected to a first source of liquid under pressure,consisting, in the example illustrated, of an hydraulic accumulator 64.The other compartment, 65 of the jack 59 is controlled, in the samemanner as in Figure 13, by two calibrated orifices 55 and 56, the actionof which is selected by nonreturn valves 57 and 58 respectively. Thesupply to or the drainage from the jack 65 are eifected under thecontrol of a set of valves'66 supplied from a second source of liquidunder pressure consisting, for example, of a hydraulic accumulator 67fed by a pump 68 from a reservoir 69. In Figure 16, the control jack 70is differential, that is to say it comprises a cylindrical compartment71 and an annular compartment 72, the latter being permanently incommunication, through pipes 73, 74 and 75, with a source of liquidunder pressure consisting of a hydraulic accumulator 76 fed by a pump 77from a reservoir 73. The cylindrical compartment 71 of the jack 79 maybe brought into communication either with the accumulator 76, or withthe reservoir 78, under the control of a set of valves 79. In thisembodiment, two calibrated orifices 8t) and 81 control respectively andexclusively, as a result of the presence of non-return valves, 82 and 83respectively, the former the drainage of the compartment 71 and thelatter the supply to the said compartment.

Figure 17 illustrates a control device identical with that in Figure 2except that it only comprises one calibrated orifice 24 controlling the.supply to the compart ment 87 of the jack 7.

In a similar manner, Figure 18 illustrates a device identical with thatin Figure 13, except that only the drainage from the compartment 42 iscontrolled by an orifice 56, a non-return valve 58 forcing the drainagedelivery to pass through the calibrated orifice 56 while it allows thesupply delivery to pass freely through a pipe 84 bypassing thecalibrated orifice 56.

The invention is in no way limited to the examples described andillustrated; it may be modified in many ways available to one skilled inthe art, according to the applications envisaged and without goingoutside the scope of the invention.

In particular, although, as already indicated, the control may beapplied indiscriminately either to the supply to or to the dischargefrom a jack, for either stroke of the movable contact of acircuit-breaker, nevertheless, in certain cases, it is a greateradvantage to control the circuit-breaking stroke by inserting thecalibrated orifices according to the invention in the evacuation systemof the jack to enable the said orifices to play their stabilizing parteven in the presence of parasitic forces acting in the direction of thecircuit-breaking stroke.

Furthermore, in Figures 15 and 16, the control of the supply and of theevacuation could be effected equally well in respect of the compartments63 (Figure 15) and 72 (Figure 16) as in respect to the compartments 65(Figure 15) and 71 (Figure 16) as illustrated.

What is claimed is:

1. In combination, with a movable member adapted to be moved in twodirections, a liquid pressure motor operably coupled with said memberfor moving the same in at least one of said two directions, a source ofliquid under pressure, conduit means in communication between saidsource and motor for conducting liquid under pressure thereto, controlvalve means in said conduit means operable when open to permit liquidunder pressure to flow from source to said motor to initiate movement ofsaid member in said at least one direction, said source being under aconstantly available pressure far in excess of that required to movesaid member at a speed higher than the optimum speed desired, and acalibrated permanently open restriction means formed by a sharp-edgedorifice constituting a speed limiting orifice disposed in said conduitmeans between said control valve and said motor and operable toestablish flow characteristics in the conduit means to apply a brakingeffect on said member that increases at a rate which is higher than therate of increase of the speed of movement of the liquid in the conduitmeans without adversely limiting the initial acceleration of the member.

2. In combination with a movable member adapted to be moved in oppositedirections relative to a desired position, a piston and cylinder means,one of said means being permanently kinematically connected to saidmember, a source of liquid under a constantly available pressure, forceapplying means for normally urging said memher to move in one of saidtwo directions at a speed higher than the optimum speed desired, a tank,valve controlled conduit means operable when open to respectivelyprovide communication between said source and said cylinder, or betweensaid cylinder and said tank, whereby flow of liquid under pressure fromsaid source to said cylinder etfects movement of said member in theother of said two directions, said source being under such pres sure asto be capable of moving said member at a speed higher than the optimumspeed desired, and when said tank is in communication with said cylindersaid force applying means effecting movement of said member in said onedirection, said member being normally retained in said desired positionby pressure of liquid in said cylinder, and in each of said conduitmeans a calibrated permanently open restriction means formed by asharpedged orifice constituting a speed limiting orifice opera- 11 bleto establish flow characteristics in the conduit means to apply abraking effect on said memberthat increases at a rate which is higher.than the rate of increase of the speed of movement of the liquid in theconduit means, without adversely limiting th'e initial acceleration ofthe member.

3. In combination with a movable member adapted to be moved inoppositedirections relative to a desired position, a piston and cylinder means,one or" said means being permanently kinematically connected to saidmember, a source of liquid under a constantly available pressure, forceapplying means for normally urging said member to move in one of saidtwo'directions at a speed higher than the optimumspeed desired, a tank,conduit means including portions operable when open to respectivelyprovide communication between said source and at least one end of saidcylinder, or between said end of said cylinder and said tank, wherebyflow of liquid under pressure from said source to said one end of thecylinder eifects movement of said member in the other of said twodirections, valve means controlling said conduit means, said sourcebeing under such pressure as to be capable of moving said member at aspeed higher than the optimum speed desired, and when said tank is incommunication with said cylinder said force applying means eitectingmovement of said member in said one direction, said member beingnormally retained in said desired position by pressure of liquid in saidcylinder, and in at least one portion of said conduit means a calibratedpermanently open restriction means formed by a sharp-edged orificeconstituting a speed limiting orifice operable to establish flowcharacteristics in the conduit means to apply a braking eifect on saidmember that increases at a rate which is higher than the rate ofincrease of the speed of movement of the liquid in the conduit means,without adversely limiting the initial acceleration of the member.

4. In combination with a movable member adapted to be moved in oppositedirections relative to a desired position, a piston and cylinder means,one of said means being permanently kinematically connected to said member, a source of liquid under a constantly available pressure, forceapplying means for normally urging said member to move in one of saidtwo directions at a speed higher than the optimum speed desired, a tank,conduit 12 a means including portions operable when open to respectivelyprovide communication between said source and at least one end of saidcylinder, or between said end ofsaid cylinder andsaid tank, whereby flowof liquid under pressure from said source to said one end of thecylinder effects movement of said member in the other of said twodirections, manually operable valve means controlling said conduitmeans, said source being under such pressure as to be capable of movingsaid member at a speed higher than the optimum speed desired, and whensaid tank is in communication with said cylinder said force applyingmeans efiecting movement of said memher in said one direction, saidmember being normally retained in said desired position by pressure ofliquid in said cylinder, and in each portion of said conduit meansbetween said manually operable valve means and said one end of thecylinder, a calibrated permanently open restriction means formed by asharp-edged orifice constituting a speed limiting orifice operable toestablish flow characteristics in the conduit means to apply a brakingeffect on said member that increases at a rate which is higher than therate of increase of the speed of movement of the liquid in the conduitmeans, without adversely limiting the initial acceleration of themember.

7 References Cited in the file of this patent UNITED STATES PATENTS674,858 Trier May 28, 1901 353,785 Henry May 14, 1907 1,037,039 MurphyAug. 27, 1912 1,993,195 Temple Mar. 5, 1935 2,127,501 Dall Aug. 23, 19382,275,872 Trencham et al. Mar. 10, 1942 2,523,572 ians son Sept. 26,1950 2,533,559 Chipman Dec. 12, 1.950 2,548,221 Kelle Apr. 10, 19512,669,628 I Van Sickle Feb. 16, 1954 2,736,295 Peek Feb. 28, 1956FOREIGN PATENTS 726,789 Germany Oct. 26, 1942 1,056,143 France Oct. 21,1953 1,098,565 France Mar. 9, 1955

